How to Retrieve Code from Docker Images

In the fast-paced world of development, it's not uncommon to find yourself needing to extract code or data from a running Docker container. Whether you need to debug an issue, retrieve a piece of code, or simply explore the state of your application, accessing the content inside a Docker container can be a lifesaver. Here's a step-by-step guide on how to bring back any code from Docker images.

Step 1: Enter into Docker Shell

The first step is to access the shell of your running Docker container. This allows you to interact with the container as if you were logged into a separate machine.

docker exec -it CONTAINER_ID sh        

Replace CONTAINER_ID with the actual ID of your container. You can find the container ID by running docker ps which lists all running containers.

Step 2: Add OpenSSH in Docker Container

Once you're inside the Docker container, you need to install the OpenSSH client. This tool will enable secure file transfer capabilities.

apt update
apt add openssh-client        

These commands use the Alpine package manager (`apk`) to update the package list and install the OpenSSH client. If you're using a different base image, you might need to use a different package manager (`apt` for Debian-based images).

Step 3: Enable SSH on Your Server

Next, you need to ensure that the SSH service is running on the server to which you want to transfer files. This involves installing the OpenSSH server and configuring the firewall to allow SSH connections.

sudo apt update
sudo apt install openssh-server
sudo systemctl enable ssh
sudo systemctl start ssh
sudo ufw allow 22/tcp
sudo ufw enable        

These commands will update the package list, install the OpenSSH server, enable it to start on boot, start the service, and configure the firewall to allow SSH traffic on port 22.

Step 4: Transfer Files from Docker Container to Server

With SSH enabled on your server and the OpenSSH client installed in your Docker container, you can now transfer files using scp. This command securely copies files and directories from your Docker container to your server.

scp -r . server_user_name@server_ip:destination_server_folder        

Replace server_user_name with your server's username, server_ip with your server's IP address, and destination_server_folder with the path to the folder where you want to transfer the files.